1. Field of the Invention
The present invention relates to a crimping terminal, especially a crimping form of the terminal for crimping a wire barrel of a crimping terminal to a conductive core portion of an aluminum electric wire (an aluminum electric wire or an aluminum alloy electric wire).
2. Description of Related Art
Recently, use of an aluminum electric wire has been demanded for weight reduction and recycling purposes for an automobile and such. Compared to a conventional copper electric wire, the aluminum electric wire has lower mechanical strength and lower meltdown temperature. Also oxidization of the surface thereof is easily produced on respective twisted core wires constituting the aluminum electric wire. Therefore, constriction resistance is generated when electric current flows only in a specific core wire, which may cause a blowout of the wire or continuity or contact failure.
Japanese Patent Publication No. 2005-50736 (FIG. 9) discloses a technique, explained herein after, which can be employed to prevent above-described problems. FIG. 3 shows a conventional art disclosed therein, which shows a crimping terminal 1 for an aluminum electric wire 2 having a box-shaped electrical contact portion 3 and a wire connecting portion 4 continued from the electrical contact portion 3. The wire connecting portion 4 has an insulation barrel 6 and a wire barrel 8 (both shown in a crimped condition) to be crimped to a covered portion 5 and a conductive core portion 7 of the aluminum wire 2, respectively. When the wire barrel 8 is crimped to the conductive core portion 7, a conduct-purpose crimping portion 9 and a wire-hold crimping portion 10 are formed at a crimping portion of the wire barrel 8.
The conduct-purpose crimping portion 9 is provided in the vicinity of the electrical contact portion 3, and the wire-hold crimping portion 10 is provided near to the insulation barrel 6. The conduct-purpose crimping portion 9 is formed by a large crimping force (caulking force), so it breaks an oxidized surface of the aluminum electric wire 2, ensuring a sufficient conduction with the conductive core portion 7 of the aluminum electric wire 2. On the other hand, the wire-hold crimping portion 10 is formed with a smaller crimping force compared to that of the conduct-purpose crimping portion 9, thus it can hold the conductive core portion 7 of the aluminum electric wire 2 for a long period of time. Therefore, the wire barrel 8 is formed slant from the conduct-purpose crimping portion 9 to the wire-hold crimping portion 10 so as to make the crimp height increase from the conduct-purpose crimping portion 9 towards the insulation barrel 6, forming an inclination 11 which is inclined at a constant angle. Bell mouths 12 are formed at both longitudinal ends of the crimping portion including the conduct-purpose crimping portion 9 and the wire-hold crimping portion 10.
However, since the inclination 11 of the above-described conventional art is formed straight, the crimping force (compression ratio) is not strictly adjusted when crimped. Thus, it is ambiguous whether or not mechanical connection reliability of the crimping portion of the wire barrel is securely ensured. In fact, the above-described conventional art retains a problem regarding to ensuring the secure mechanical connection of the crimping portion of the wire barrel.
In view of above-described problem, an object of the present invention is to provide a crimping terminal formed so as to improve the mechanical connection reliability of the crimping portion of the wire barrel.